Ion exchangeable glasses

ABSTRACT

An ion exchangeable glass that is free of lithium and comprising 0.1-10 mol % P 2 O 5  and at least 5 mol % Al 2 O 3 . The presence of P 2 O 5  enables the glass to be ion exchanged more quickly and to a greater depth than comparable glasses that do not contain P 2 O 5 .

BACKGROUND

Chemically strengthened glasses are used in touch screen and applications. Currently, many glasses must be ion exchanged by immersion in a molten salt bath for 8 to 10 hours to achieve a compressive layer of more than 50 microns deep with at least 500 MPa compressive stress at the surface.

SUMMARY

An ion exchangeable glass comprising 0.1-10 mol % P₂O₅ is provided. The presence of P₂O₅ enables the glass to be ion exchanged more quickly and to a greater depth than comparable glasses that do not contain P₂O₅.

Accordingly, one aspect of the disclosure is to provide an ion exchangeable aluminosilicate glass. The ion exchangeable aluminosilicate glass is free of lithium and comprises 0.1-10 mol % P₂O₅ and at least 5 mol % Al₂O₃. The glass has a liquidus viscosity of at least 100 kpoise.

Another aspect of the disclosure is to provide a method of strengthening an ion exchangeable aluminosilicate glass. The method comprises providing an ion exchangeable aluminosilicate glass comprising 0.1-10 mol % P₂O₅, at least 5 mol % Al₂O₃, and a plurality of first monovalent cations; and exchanging at least a portion of the first monovalent cations with second monovalent cations to a depth of at least 20 μm in the glass article, wherein the second monovalent cations are different from the first monovalent cations. The exchanging of the second actions for the first cations in the glass article creates a compressive stress in a region adjacent to a surface of the glass article.

These and other aspects, advantages, and salient features will become apparent from the following detailed description, the accompanying drawings, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a glass sheet strengthened by ion exchange;

FIG. 2 is a plot of depth of compressive layer and compressive stress in ion exchanged alkali aluminosilicate glasses as a function of P₂O₅ content;

FIG. 3 is a plot of weight change of ion exchanged alkali aluminosilicate glasses as a function of P₂O₅ content;

FIG. 4 is a plot of depth of compressive layer and compressive stress as a function of P₂O₅ addition to an alkali aluminosilicate glass; and

FIG. 5 is a plot of potassium diffusivity as a function of P₂O₅ concentration in alkali aluminosilicate glass.

DETAILED DESCRIPTION

In the following description, like reference characters designate like or corresponding parts throughout the several views shown in the figures. It is also understood that, unless otherwise specified, terms such as “top,” “bottom,” “outward,” “inward,” and the like are words of convenience and are not to be construed as limiting terms. In addition, whenever a group is described as comprising at least one of a group of elements and combinations thereof, it is understood that the group may comprise, consist essentially of, or consist of any number of those elements recited, either individually or in combination with each other. Similarly, whenever a group is described as consisting of at least one of a group of elements or combinations thereof, it is understood that the group may consist of any number of those elements recited, either individually or in combination with each other. Unless otherwise specified, a range of values, when recited, includes both the upper and lower limits of the range. Unless otherwise specified, all concentrations of elements and compounds are expressed in mole percent (mol %).

Referring to the drawings in general and to FIG. 1 in particular, it will be understood that the illustrations are for the purpose of describing particular embodiments and are not intended to limit the disclosure or appended claims thereto. The drawings are not necessarily to scale, and certain features and certain views of the drawings may be shown exaggerated in scale or in schematic in the interest of clarity and conciseness.

Chemically strengthened glasses are used in display applications such as touch screens and ruggedized displays in mobile consumer electronics, including cell phones, mobile internet devices, entertainment devices, laptop and notebook computers, and the like. Some glasses, such as aluminosilicate glasses and alkali aluminosilicate glasses, can be strengthened chemically by a process known as ion exchange. In this process, ions in the surface layer of the glass are replaced by—or exchanged with—larger ions having the same valence or oxidation state as the ions in the surface layer of the glass. In those embodiments in which the glass comprises, consists essentially of, or consists of an alkali aluminosilicate glass, ions in the surface layer of the glass and the larger ions are monovalent alkali metal cations, such as Li⁺ (when present in the glass), Na⁺, K⁺, Rb⁺, and Cs⁺. Alternatively, monovalent cations in the surface layer may be replaced with monovalent cations other than alkali metal cations, such as Ag⁺, Cu⁺, Tl⁺, or the like. In addition, such cations can be initially present in the glass itself.

Ion exchange processes typically include immersing the aluminosilicate glass in a molten salt bath containing the larger ions to be exchanged with the smaller ions in the glass. By way of example, ion exchange of alkali metal-containing glasses may be achieved by immersion in at least one molten salt bath containing a salt such as, but not limited to, nitrates, sulfates, and chlorides of the larger alkali metal ion. The temperature of the molten salt bath is typically in a range from about 380° C. up to about 450° C., and immersion times range from about 2 hours up to about 16 hours. Such ion exchange treatments typically result in strengthened alkali aluminosilicate glasses having an outer surface layer (also referred to herein as the “depth of layer” or “DOL”) that is under compressive stress (CS).

A cross-sectional view of a glass sheet strengthened by ion exchange is schematically shown in FIG. 1. Strengthened glass sheet 100 has a thickness t, a first surface 110 and second surface 120 that are substantially parallel to each other, central portion 115, and edges 130 joining first surface 110 to second surface 120. Strengthened glass sheet 100 is chemically strengthened by ion exchange, and has strengthened surface layers 112, 122 extending from first surface 110 and second surface 120, respectively, to depths d₁, d₂, below each surface. Strengthened surface layers 112, 122 are under a compressive stress, while central portion 115 is under a tensile stress, or in tension. The tensile stress in central portion 115 balances the compressive stresses in strengthened surface layers 112, 122, thus maintaining equilibrium within strengthened glass sheet 100. The depths d₁, d₂ to which the strengthened surface layers 112, 122 extend are generally referred to individually as the “depth of layer (DOL).” A portion 132 of edge 130 may also be strengthened as a result of the strengthening process. Thickness t of strengthened glass sheet 100 is generally in a range from about 0.1 mm up to about 3 mm. In one embodiment, thickness t is in a range from about 0.5 mm up to about 1.3 mm. Whereas a planar glass sheet 100 is shown in FIG. 1, other non-planar configurations, such as a three dimensional form, are possible. In addition, a single surface of the glass sheet can be strengthened by ion exchange.

In order to achieve a desired depth of compressive layer of more than 50 μm and/or a desired compressive stress of at least 500 MPa at the surface, alkali aluminosilicate glasses typically undergo chemical strengthening by ion exchange ion exchange for 8 to 10 hours.

Described herein is an ion exchangeable aluminosilicate glass and articles made therefrom that are capable of undergoing ion exchange at rates that are up to four times faster than those previously observed for such glasses. The aluminosilicate glasses are ion exchangeable with at least one of sodium, potassium, rubidium, cesium, copper, silver, thallium, and the like.

The glasses described herein is substantially free of lithium (i.e., lithium is not actively added to the glass during initial batching or subsequent ion exchange, but may be present as an impurity) and comprises from about 0.1 mol % up to about 10 mol % P₂O₅ and at least 5 mol % Al₂O₃. The glass has a liquidus viscosity of at least 100 kpoise and, in some embodiments, at least 135 kpoise, which allows the glass to be formed by down-draw methods (e.g., slot-draw or fusion-draw) methods known in the art. In selected embodiments, the glass has a liquidus viscosity of at least 2 megapoise (Mpoise).

In some embodiments, the P₂O₅ concentration is less than or equal to the difference between the total concentration of metal oxide modifiers Σ(R₂O) and the Al₂O₃ concentration—i.e., P₂O₅≦[Σ(R₂O)−Al₂O₃]. In one embodiment, the glass is an alkali aluminosilicate glass that includes at least one monovalent metal oxide modifier—e.g., Ag₂O, Na₂O, K₂O, Rb₂O, and/or Cs₂O. In such glasses, the P₂O₅ concentration is less than or equal to the difference between the total concentration of alkali metal oxide modifiers and the Al₂O₃ concentration—i.e., P₂O₅≦[(Na₂O+K₂O+Rb₂O+Cs₂O)−Al₂O₃]. When the P₂O₅ content exceeds the excess amount of alkali modifiers, refractory batch stones and aluminum phosphate inclusions begin to form in the glass. Alkaline earth oxides like MgO, CaO, SrO, and BaO can cause phase separation and/or devitrification. Consequently, the total concentration of alkaline earth oxides should be limited to approximately no more than one half of the P₂O₅ concentration; i.e., ΣR′O(R=Mg, Ca, Ba, Sr)≦0.5 P₂O₅. Similarly, in those embodiments where the modifiers are other metal oxides such as Ag₂O. Cu₂O, or Tl₂O, the P₂O₅ concentration is less than or equal to the difference between the total concentration of metal oxide modifiers and the Al₂O₃ concentration—i.e., P₂O₅≦[(Ag₂O+Tl₂O+Cu₂O−Al₂O₃)].

In one embodiment, the ion exchangeable aluminosilicate glass is an alkali aluminosilicate glass that comprises, consists essentially of, or consists of: 56-72 mol % SiO₂; 5-18 mol % Al₂O₃; 0-15 mol % B₂O₃; 0.1-10 mol % P₂O₅; 3-25 mol % Na₂O; and 0-5 mol % K₂O; and is free of lithium. The alkali aluminosilicate glass can, in some embodiments, further include at least one of: 0-4 mol % CaO; 0-1 mol % MgO; and up to 0.5 mol % SnO₂. Exemplary compositions of the glasses described herein are listed in Table 1. Physical properties, including strain, anneal, and softening points, coefficient of thermal expansion (CTE), density, molar volume, stress optical coefficient (SOC), and liquidus temperature of these glasses are listed in Table 2. Table 3 lists compressive stresses (CS), depth of layer (DOL), and potassium diffusivity (D) for selected glasses after ion exchange for 8 hours in a KNO₃ bath at either 410° C. or 370° C. In another embodiment, the glass is an aluminosilicate glass that comprises, consists essentially of, or consists of: 56-72 mol % SiO₂; 5-18 mol % Al₂O₃; 0-15 mol % B₂O₃; 0.1-10 mol % P₂O₅; and 2-20 mol % Ag₂O. This glass as well, in some embodiments, is free of lithium.

The presence of P₂O₅ in the aluminosilicate or alkali aluminosilicate glass accelerates the rate of ion exchange of larger cations for smaller cations present in the glass. In particular, the presence of P₂O₅ accelerates the rate of ion exchange of K⁺ ions for Na⁺ ions in alkali aluminosilicate glasses. The data listed in Tables 1-3 show the effect of P₂O₅ concentration on ion exchange and physical properties of alkali aluminosilicate glasses. Curves a-d in FIG. 2 show the increase in DOL in ion exchanged alkali aluminosilicate glasses with increasing P₂O₅ content, whereas curves e-h show the decrease in compressive stress CS with increasing P₂O₅ content for ion exchanged alkali aluminosilicate glasses for different bath temperatures (410° C., 370° C.) and times (8, 15, and 64 hours). Points 1 and 2 represent the compressive stress and depth of layer, respectively, of an alkali aluminosilicate glass reference sample (Example 1 in Tables 1-3) that had been ion exchanged and annealed and that does not contain P₂O₅. The weight gains of selected ion exchanged alkali aluminosilicate glasses listed in Table 3 are plotted as a function of P₂O₅ content in FIG. 3. The weight gains shown in FIG. 3 were measured for different ion exchange conditions—for different bath temperatures (410° C., 370° C.) and times (8, 15, and 64 hours)—and reflect the extent of exchange of heavier K⁺ ions for Na⁺ ions in the glasses. Point 3 in FIG. 3 represents the weight change observed for an alkali aluminosilicate glass reference sample (sample 1 in Tables 1-3) that does not contain P₂O₅ and had been annealed and ion exchanged. The steady increase in weight with P₂O₅ content indicates that the presence of P₂O₅ in the glasses described herein promotes and/or accelerates the exchange of K⁺ for Na⁺ ions. FIG. 4 is a plot the effect of P₂O₅ addition on depth of layer and compressive stress of alkali aluminosilicate glasses having the composition 66 mol % SiO₂, 25 mol % Na₂O, and 9 mol % Al₂O₃. As can be seen in FIG. 4, the addition of 2 mol % P₂O₅ results in a 50% increase in depth of layer.

The ion exchange data listed in Table 3 and plotted in FIG. 2 show that 4 mole % P₂O₅ is sufficient to double the DOL in alkali aluminosilicate glasses. Since DOL increases as approximately the square root of time and diffusivity, this implies that the coupled K⁺

Na⁺ diffusivity is increased by a factor of four. Thus, the addition of P₂O₅ to a glass can decrease the time needed to achieve a given depth of layer by a factor of four. The diffusivity D of K⁺ ions in a phosphorus-free annealed alkali aluminosilicate glass (sample 1 in Tables 1-3) is given by the equation D=exp(−3.8965−13240/T), where the diffusivity D is expressed in (cm²/sec) and the temperature T is expressed in degrees Kelvin (K). At 410° C. (683 K), which is a temperature at which the exchange of K⁺ ions for Na⁺ ions is typically carried out, the diffusivity of K⁺ ions in the glasses described herein is 7.8×10⁻¹¹ cm²/sec. The equation provided above is derived for annealed glasses. As previously described herein, alkali aluminosilicate glasses can be formed by down-draw processes such as fusion-draw processes. The diffusivity of K⁺ ions in fusion-formed glasses can be taken to be about 1.4 times greater than the diffusivity of these ions in annealed glass. Thus, the diffusivity of K⁺ ions in fusion-formed alkali aluminosilicate glasses is estimated to be about 1.1×10⁻¹⁰ cm²/sec at 400° C. (673 K). The faster K⁺

Na⁺ ion exchange rates that are enabled by the enhanced diffusivity of alkali metal ions in the phosphorus-containing glasses described herein have been previously achieved only with smaller ions, such as Na⁺

Li⁺, which produces a lower compressive stress than K⁺

Na⁺ ion exchange. Thus, the compositions described herein permit compressive stresses achievable with K⁺

Na⁺ ion exchange to be carried out at the speed or rate of Na⁺

Li⁺ ion exchange. In one embodiment, the alkali aluminosilicate glasses described herein, when immersed in a KNO₃ molten salt bath at 410° C. for less than six hours, are capable of exchanging K⁺ for Na⁺ in the glass to a depth of at least 50 μm. In some embodiments, the alkali aluminosilicate glasses described herein, when ion exchanged, have a compressive layer with a depth of layer of at least 20 μm and a compressive stress of at least 400 MPa. In other embodiments, the glasses are ion exchanged to a depth of layer of up to 150 μm, and in still other embodiments, the glasses are ion exchanged to a depth of layer of up to 100 μm.

Potassium diffusivity is plotted as a function of P₂O₅ concentration in two alkali aluminosilicate glasses in FIG. 5. Data for two glasses containing either 4 mol % (a in FIG. 5) or 8 mol % (b in FIG. 5) B₂O₃ are plotted in FIG. 5. The addition of 4 mol % P₂O₅, increases the K⁺ diffusivity in the glasses containing 4 mol % B₂O₃ by about 50%, whereas the addition of the same amount of P₂O₅ to the glass glasses containing 8 mol % B₂O₃ yields an increase in K⁺ diffusivity of about one third. The lower increase in diffusivity observed in the latter glass can be attributed to the increased amount of B₂O₃, which tends to reduce K⁺ diffusivity in glass.

The addition of P₂O₅ to alkali aluminosilicate glasses also can be used to obtain low liquidus temperatures. All the glasses listed in Table 1 have liquidus temperatures of less than about 700° C. Glass #2 has a liquidus viscosity over 248 million Poise (MP), and is therefore formable by down-draw methods, such as slot-draw and fusion draw methods that are known in the art. Alternatively, the glasses described herein are also formable by other methods, such as float, molding, and casting methods that are known in the art. The presence of P₂O₅ also decreases the viscosity of the glass at high temperatures. An addition of 2 mole % P₂O₅ is capable of lowering the 200P temperature of the alkali aluminosilicate glass by 50° C., which facilitates melting and fining of the glass.

A method of strengthening a glass article is also provided. A glass article comprising an aluminosilicate glass comprising 0.1-10 mol % P₂O₅ and at least 5 mol % Al₂O₃, such as those glasses described herein, is first provided. The glass also includes a plurality of first monovalent cations such as, for example, an alkali metal cation or a monovalent cation such as Ag⁺, Cu⁺, Tl⁺, or the like. In some embodiments, the aluminosilicate glass is an alkali aluminosilicate glass is lithium-free and comprises, consists essentially of, or consists of: 56-72 mol % SiO₂; 5-18 mol % Al₂O₃; 0-15 mol % B₂O₃; 0.1-10 mol % P₂O₅; 3-25 mol % Na₂O; and 0-5 mol % K₂O. The alkali aluminosilicate glass can, in some embodiments, further include at least one of 0-4 mol % CaO; 0-1 mol % MgO; and up to 0.5 mol % SnO₂. The glass has a liquidus viscosity of at least 100 kP and, in some embodiments, at least 135 kP, and can be made by those down-draw methods (e.g., slot-draw, fusion-draw, or the like). In addition, the alkali aluminosilicate glass possesses those properties (strain, anneal, and softening points, coefficient of thermal expansion (CTE), density, molar volume, stress optical coefficient (SOC), and liquidus temperature) previously described herein and reported in Table 1b. In other embodiments, the glass is an aluminosilicate glass comprising, consisting essentially of, or consisting of: 56-72 mol % SiO₂; 5-18 mol % Al₂O₃; 0-15 mol % B₂O₃; 0.1-10 mol % P₂O₅; and 2-20 mol % Ag₂O.

In the next step, second monovalent cations are exchanged for—or replaces—at least a portion the first monovalent cations in a region adjacent to the surface of the glass. The second monovalent cation is different from the first cation and, in some embodiments, larger than the first monovalent cation. In those instances where the second cation is larger than the first cation, the replacement of first cations with second cations in the region adjacent to the surface of the glass creates a compressive stress in that region. In those instances where the glass is an alkali aluminosilicate glass, for example, K⁺ ions are exchanged for Na⁺ ions in the alkali aluminosilicate glass by ion exchange, using those methods previously described herein. Potassium ions are ion exchanged for Na⁺ ions to a depth of up to up to 100 μm in the glass article and, in some embodiments, up to 150 μm. In some embodiments, K⁺ ions are exchanged for Na⁺ ions to a depth of at least 20 μm in the glass article, in other embodiments, at least 50 μm, and in still other embodiments, to a depth of 150 μm.

The glasses described herein can be formed into planar sheets for use as display windows, cover plates, screens, structural features, and the like, for applications such as, but not limited to, touch screens and mobile electronic devices, including telephones and other communication devices, entertainment devices, and hand-held, laptop and notebook computers. In other embodiments, the alkali aluminosilicate glass can be formed into three dimensional, non-planar shapes, such as curved sheets or the like.

TABLE 1 Compositions of alkali aluminosilicate glasses. Sample mol % Number SiO₂ Al₂O₃ B₂O₃ Na₂O K₂O MgO CaO SnO₂ P₂O₅ As₂O₃ 1 66.4 10.31 0.602 14.02 2.1 5.76 0.58 0.207 0 0 2 66.4 10.31 0.602 14.02 2.1 5.76 0.58 0.207 0 0 19 61.53 11.51 5.73 15.30 1.93 0.02 0.05 0.10 3.84 0.00 20 60.36 11.29 4.69 15.96 1.89 0.02 0.05 0.09 5.65 0.00 21 59.24 11.09 4.60 15.66 1.85 0.02 0.05 0.09 7.39 0.00 22 58.16 10.88 4.51 15.38 1.82 0.02 0.05 0.09 9.07 0.00 23 61.52 12.00 4.78 15.79 1.93 0.00 0.05 0.10 3.83 0.00 24 61.53 12.48 4.77 15.30 1.93 0.00 0.05 0.10 3.84 0.00 25 61.52 13.43 4.78 14.35 1.92 0.00 0.05 0.10 3.84 0.00 26 61.52 11.51 4.77 15.31 1.92 0.97 0.05 0.10 3.84 0.00 27 61.52 11.51 4.78 14.35 1.93 1.94 0.05 0.10 3.84 0.00 28 61.51 11.51 4.77 13.39 1.93 2.91 0.05 0.10 3.84 0.00 29 63.96 11.97 4.97 15.92 2.00 0.02 0.05 0.10 1.00 0.00 30 63.96 11.97 4.96 15.93 0.00 0.02 0.05 0.10 3.00 0.00 31 63.97 11.98 5.96 15.43 0.80 0.02 0.05 0.10 1.60 0.00 32 63.96 11.97 5.96 14.93 2.00 0.02 0.05 0.10 1.00 0.00 33 63.98 11.97 5.96 12.93 2.00 0.02 0.04 0.10 2.99 0.00 34 63.98 11.97 5.96 10.95 2.00 0.02 0.04 0.10 4.98 0.00 35 63.96 12.08 5.96 15.43 0.80 0.02 0.05 0.10 1.60 0.00 36 63.98 12.22 7.45 14.68 0.05 0.02 0.05 0.10 1.00 0.00 37 63.99 12.38 8.93 13.93 0.20 0.02 0.05 0.10 0.40 0.00 38 63.79 11.94 5.94 15.87 1.99 0.02 0.05 0.10 0.30 0.00 39 63.65 11.92 5.93 15.84 1.99 0.02 0.05 0.10 0.50 0.00 40 63.46 11.88 5.91 15.80 1.98 0.02 0.05 0.10 0.79 0.00 41 63.97 11.47 9.93 12.44 1.00 0.02 0.05 0.12 1.00 0.00 42 63.97 10.48 9.93 12.43 1.00 0.02 0.05 0.12 2.00 0.00 43 64.04 13.59 8.11 13.54 0.51 0.02 0.07 0.10 0.00 0.00 44 64.52 11.55 7.99 13.38 0.50 0.02 0.07 0.10 1.86 0.00 45 64.81 9.57 7.94 13.30 0.49 0.02 0.06 0.10 3.69 0.00 46 64.08 15.63 3.97 15.60 0.52 0.01 0.07 0.10 0.00 0.00 47 64.44 13.57 4.04 15.35 0.51 0.02 0.07 0.10 1.88 0.00 48 64.84 11.55 4.00 15.26 0.50 0.02 0.06 0.10 3.65 0.00 49 63.95 13.71 5.95 13.67 0.50 0.02 0.10 0.10 2.00 0.00 50 63.93 13.71 3.98 13.68 0.50 0.02 0.10 0.10 3.99 0.00 51 63.94 11.96 3.97 15.42 0.50 0.02 0.10 0.10 3.99 0.00 52 63.94 12.96 3.97 14.42 0.50 0.02 0.10 0.10 3.99 0.00 53 63.95 13.96 3.97 13.42 0.50 0.02 0.09 0.10 3.99 0.00 54 63.93 14.96 3.98 12.43 0.50 0.02 0.09 0.10 3.99 0.00 55 60.18 12.48 9.93 15.63 0.60 0.02 0.05 0.10 1.00 0.00 56 58.19 12.48 9.93 15.63 0.60 0.02 0.04 0.10 3.00 0.00 57 60.90 12.42 9.88 15.55 0.60 0.02 0.05 0.10 0.50 0.00 58 60.59 12.36 9.83 15.47 0.60 0.02 0.05 0.10 0.99 0.00 59 59.43 12.11 9.64 15.17 0.58 0.02 0.04 0.10 2.91 0.00 60 58.30 11.88 9.47 14.88 0.57 0.02 0.04 0.09 4.76 0.00 61 61.85 11.63 7.72 15.17 0.58 0.02 0.04 0.10 2.91 0.00 62 61.20 12.48 9.43 15.63 0.60 0.02 0.05 0.10 0.50 0.00 63 61.19 12.48 8.94 15.63 0.60 0.02 0.05 0.10 1.00 0.00 64 61.18 12.47 6.96 15.63 0.60 0.02 0.04 0.10 3.00 0.00 65 61.19 12.47 4.97 15.62 0.60 0.02 0.04 0.10 4.99 0.00 66 60.20 12.48 9.93 15.63 0.60 0.02 0.05 0.10 1.00 0.00 67 58.21 12.48 9.93 15.63 0.60 0.02 0.04 0.10 3.00 0.00 68 66 14 0 20 0 0 0 0 2 0.4 69 66 14 0 20 0 0 0 0 1 0.4 70 64 14 0 20 0 0 0 0 2 0.4 71 65 14 0 20 0 0 0 0 1 0.4 72 66 9 0 25 0 0 0 0 2 0.4 73 66 9 0 25 0 0 0 0 1 0.4 74 64 9 0 25 0 0 0 0 2 0.4 75 65 9 0 25 0 0 0 0 1 0.4

TABLE 2 Physical properties of alkali aluminosilicate glasses. Molar & CTE of Density spec. Strain Annealing Softening glass < at volume at Liquidus SOC Sample Point, Point, point, Tg × 10⁷ 20° C., 20° C., Liquidus, viscosity, 200p T, (nm/cm/ Number ° C. ° C. ° C. K⁻¹ g/cm³ cm³/mol ° C. poise ° C. Mpa) 1 31.8 2 28.8 19 505.3 550.6 762.2 87.81 2.409 28.89 <720 CTE of Density Molar Strain Annealing Softening glass < at volume at Liquidus SOC Sample Point, Point, point, Tg × 10⁷ 20° C., 20° C., Liquidus, viscosity, 200p T, (nm/cm/ Number ° C. ° C. ° C. K⁻¹ g/cm³ cm³/mol ° C. (poise) ° C. Mpa) 20 492.4 539.1 755.5 91.28 2.405 29.47 <725 21 477.2 524.5 755.8 92.071 2.396 30.13 <710 22 475 526.1 749.6 93.753 2.387 30.78 23 515.6 561.8 775.1 89.283 2.413 28.89 24 514.9 562.2 789.1 88.739 2.41 29.01 25 523.4 573 824.1 84.17 2.395 29.35 26 521.7 570.1 797.8 90.784 2.412 28.74 27 528.5 578.2 807.5 90.95 2.41 28.67 28 529.9 581.9 839 87.405 2.404 28.66 1070 29 527.6 570.7 761.2 89.733 2.44 27.64 820 30 535.2 580.7 789.9 85.209 2.419 28.07 860 31 533.3 580.8 807.3 83.4 2.4 28.5 730 341650833 1631.8 32 530.2 574.1 769.8 89.435 2.426 27.83 745 33 520.4 569.7 806.7 84.477 2.382 29.01 750 200196453 1669.1 34 511 564.1 838.1 76.85 2.352 30.06 35 535.5 579.9 797.8 83.959 2.412 28.05 36 532.9 579.3 800.2 79.552 2.393 28.1 37 530.8 577.8 801.7 76.669 2.376 28.14 38 522.7 564 755.2 90.762 2.447 27.36 39 525.5 567.7 760.5 89.251 2.441 27.49 40 526 569.2 761.5 88.836 2.438 27.61 41 508.2 556.2 784.6 75.484 2.356 28.58 42 499.9 547 784.9 75.695 2.358 28.73 Molar & Softening TEC of Density spec. Strain Annealing point, glass < at volume at SOC Sample Point, Point, (Littleton) Tg*1e7 20° C., 20° C., Liquidus, Liquidus 200p T, (nm/cm/ Number ° C. ° C. ° C. K{circumflex over ( )}−1 g/cm{circumflex over ( )}3 cm{circumflex over ( )}3/mol C. viscosity C. Mpa) 43 542 594 856 79 2.374 34.64 44 516 563 796 77.1 2.375 33.66 45 497 542 762 78.3 2.371 32.97 46 592 649 933 85.9 2.411 790 864900779 1690.6 32.42 47 552 603 856 84.6 2.407 760 584512466 1695.3 31.63 48 525 573 812 83.9 2.399 790 4.90E+07 1654.5 31.17 49 546 603 882 77.734 2.375 860 50 549 606 899 76.448 2.373 835 51 527 576 816 84.01 2.397 890 52 540 594 859 79.742 2.381 53 554 612 906 77.119 2.370 54 578 641 955 71.763 2.358 55 83.4 56 84.4 57 531 573 2.403 850 58 519 562 759 82 2.395 <750 3.42E+07 1550 59 512 555 2.381 <785 60 501 545 759 81.1 2.369 <820 2.87E+07 1545 61 518 563 2.389 <795 62 525 566 2.404 63 528 572 767 82.8 2.4 <785 1.03E+07 1545 64 519 565 2.393 65 517 565 803 83.3 2.386 <820 2.549E+10  1625 66 521 564 2.395 67 503 547 766 82.2 2.381 <795 68 561 609 2.45 69 570 619 2.44 70 572 621 2.45 71 569 620 2.45 72 486 530 73 479 522 2.46 74 485 528 2.46 75 479 521 2.47

TABLE 3 Physical properties of alkali aluminosilicate glasses, post-ion exchange. IX 410° C. IX 370° C. 8 hrs 8 hrs Sample CS DOL D (×10⁻¹¹ Cs DOL D (×10⁻¹¹ Number (MPa) (μm) cm²/s) (MPa) (μm) cm²/s) 1 852.864 42.497 8.170 889.87 21.85 2.159 2 942 42.5 8.170 982.6 21.8 2.159 19 565 73 23.876 688 40 7.321 20 472 97 42.453 598 54 13.393 21 390 103 47.840 496 57 14.621 22 396 61 49.022 23 610 75 25.117 718 44 8.747 24 615 73 24.237 731 44 8.885 25 644 72 23.614 752 41 7.736 26 592 70 22.248 723 40 7.152 27 644 63 17.753 736 38 6.477 28 635 59 15.702 725 33 5.061 29 694 51 11.940 828 29 3.731 30 702 58 15.090 823 33 4.832 31 659 58 15.159 788 34 5.254 32 734 49 10.775 827 27 3.259 33 591 66 19.987 703 38 6.519 34 550 40 7.329 35 731 48 10.287 875 24 2.570 36 755 39 6.879 866 21 1.924 37 766 36 5.702 926 18 1.414 38 732 39 6.772 860 20 1.801 39 730 40 7.243 862 22 2.198 40 728 44 8.763 831 24 2.708 IX 410° C. IX 370° C. 8 Hrs 8 Hrs Sample CS DOL D Cs DOL D Number (Mpa) (μm) (×10⁻¹¹) (Mpa) (μm) (×10⁻¹¹) 41 611 38 6.366 718 20 1.791 42 533 37 6.327 681 21 1.998 43 799 38 6.689 916 21 1.970 44 629 39 7.014 740 22 2.141 45 501 44 8.72 578 25 2.829 46 1053 51 11.851 1110 27 3.287 47 804 54 13.315 963 30 3.976 48 652 65 19.22 793 37 6.268 49 757 48 10.517 876 26 3.165 50 680 61 17.079 755 35 5.685 51 634 66 19.418 746 36 5.739 52 670 63 17.755 768 34 5.188 53 691 61 16.899 778 34 5.130 54 710 60 16.197 765 35 5.405 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75

While typical embodiments have been set forth for the purpose of illustration, the foregoing description should not be deemed to be a limitation on the scope of the disclosure or appended claims. Accordingly, various modifications, adaptations, and alternatives may occur to one skilled in the art without departing from the spirit and scope of the present disclosure or appended claims. 

The invention claimed is:
 1. An ion exchangeable aluminosilicate glass, the ion exchangeable aluminosilicate glass being free of lithium and comprising 1-10 mol % P₂O₅, Na₂O, and at least 5 mol % Al₂O₃, wherein 77.52 mol %≧SiO₂+Al₂O₃≧70.04 mol % and ΣR′O≦0.5 P₂O₅ (mol %), where R′=Mg, Ca, Ba, and Sr, and wherein the glass has a liquidus viscosity of at least 100 kpoise.
 2. The ion exchangeable aluminosilicate glass of claim 1, wherein the liquidus viscosity is at least 135 kpoise.
 3. The ion exchangeable aluminosilicate glass of claim 1, wherein the glass is ion exchangeable with at least one of sodium, potassium, rubidium, cesium, copper, thallium, and silver.
 4. The ion exchangeable aluminosilicate glass of claim 1, wherein potassium has a diffusivity of at least 7.8×10⁻¹¹ cm²/sec in the glass.
 5. The ion exchangeable aluminosilicate glass of claim 1, wherein potassium has a diffusivity of at least 1.1×10⁻¹⁰ cm²/sec in the glass.
 6. The ion exchangeable aluminosilicate glass of claim 1, wherein the glass has a diffusivity D>exp(−3.8965−13240/T), where the diffusivity is expressed in (cm²/sec) and T is temperature expressed in degrees Kelvin (K).
 7. The ion exchangeable aluminosilicate glass of claim 6, wherein the glass is ion exchanged.
 8. The ion exchangeable aluminosilicate glass of claim 6, wherein the glass is ion exchanged to a depth in a range from 20 μm up to 150 μm.
 9. The ion exchangeable aluminosilicate glass of claim 6, wherein the glass has an outer layer having a compressive stress of at least 200 MPa.
 10. The ion exchangeable aluminosilicate glass of claim 1, wherein the glass comprises at least one monovalent metal oxide modifier R₂O, wherein P₂O₅≦[Σ(R₂O)—Al₂O₃].
 11. The ion exchangeable aluminosilicate glass of claim 10, wherein the at least one monovalent metal oxide modifier comprises Na₂O and, optionally, at least one of K₂O, Rb₂O, Ag₂O, and Cs₂O, and wherein P₂O₅≦[(Na₂O+K₂O+Rb₂O+Ag₂O+Cs₂O)—Al₂O₃].
 12. The ion exchangeable aluminosilicate glass of claim 1, wherein the aluminosilicate glass is an alkali aluminosilicate glass comprising: 56-72 mol % SiO₂; 5-18 mol % Al₂O₃; 0-15 mol % B₂O₃; 1-10 mol % P₂O₅; 3-25 mol % Na₂O; and 0-5 mol % K₂O.
 13. The ion exchangeable aluminosilicate glass of claim 1, wherein the glass is down-drawable.
 14. The ion exchangeable aluminosilicate glass of claim 1, wherein the glass, when immersed in a KNO₃ molten salt bath at 410° C. for up to six hours, is capable of exchanging K⁺ ions for Na⁺ ions in the glass to a depth of at least 50 μm.
 15. The ion exchangeable aluminosilicate glass of claim 1, wherein the aluminosilicate glass comprises: 56-72 mol % SiO₂; 5-18 mol % Al₂O₃; 0-15 mol % B₂O₃; 1-10 mol % P₂O₅; and 2-20 mol % Ag₂O.
 16. A method of strengthening a glass article, the method comprising the steps of: a. providing the glass article, the glass article comprising an ion exchangeable aluminosilicate glass, wherein the aluminosilicate glass is free of lithium and has a liquidus viscosity of at least 100 kpoise and comprises: 1-10 mol % P₂O₅; Na₂O; and at least 5 mol % Al₂O₃, wherein 77.52 mol %≧SiO₂+Al₂O₃≧70.04 mol % and ΣR′O≦0.5 P₂O₅ (mol %), where R′=Mg, Ca, Ba, and Sr; and a plurality of first monovalent cations; and b. exchanging at least a portion of the first monovalent cations with second monovalent cations to a depth in a range from 20 μm up to 150 μm in the glass article, wherein the second monovalent cations are different from the first monovalent cations, wherein exchanging the second actions for the first cations in the glass article creates a compressive stress in a region adjacent to a surface of the glass article.
 17. The method of claim 16, wherein the first monovalent cations and second monovalent cations are alkali metal cations.
 18. The method of claim 16, wherein the step of exchanging at least a portion of the first monovalent cations with second monovalent cations comprises K⁺ ions for Na⁺ ions in the glass article to a depth of up to 150 μm in the glass article.
 19. The method of claim 16, wherein the second monovalent cations are larger than the first monovalent cations.
 20. The method of claim 16, wherein potassium has a diffusivity of at least 1.1×10⁻¹⁰ cm²/sec in the glass.
 21. The method of claim 16, wherein the glass has a diffusivity D>exp(−3.8965−13240/T), where the diffusivity is expressed in (cm²/sec) and T is temperature expressed in degrees Kelvin (K).
 22. The method of claim 16, wherein the step of providing the ion exchangeable aluminosilicate glass comprises down-drawing the ion exchangeable aluminosilicate glass.
 23. The method of claim 16, wherein the aluminosilicate glass is an alkali aluminosilicate glass comprising: 56-72 mol % SiO₂; 5-18 mol % Al₂O₃; 0-15 mol % B₂O₃; 1-10 mol % P₂O₅; 3-25 mol % Na₂O; and 0-5 mol % K₂O.
 24. The method of claim 16, wherein the aluminosilicate glass comprises: 56-72 mol % SiO₂; 5-18 mol % Al₂O₃; 0-15 mol % B₂O₃; 1-10 mol % P₂O₅; and 2-20 mol % Ag₂O.
 25. An ion exchangeable aluminosilicate glass, the ion exchangeable aluminosilicate glass being free of lithium having a liquidus viscosity of at least 100 kpoise and comprising 1-10 mol % P₂O₅, Na₂O, at least 59.24 mol % SiO₂, and greater than 11.09 mol % Al₂O₃, wherein ΣR′O≦0.5 P₂O₅(mol %), where R′=Mg, Ca, Ba, and Sr.
 26. The ion exchangeable aluminosilicate glass of claim 1, wherein the aluminosilicate glass comprises at least 59.24 mol % SiO₂, and greater than 11.09 mol % Al₂O₃.
 27. An ion exchangeable aluminosilicate glass, the ion exchangeable aluminosilicate glass being free of lithium and comprising: 56-72 mol % SiO₂; 5-18 mol % Al₂O₃; 0-15 mol % B₂O₃; 0.1-10 mol % P₂O₅; 3-25 mol % Na₂O; and 2-20 mol % Ag₂O, wherein the glass has a liquidus viscosity of at least 100 kpoise.
 28. The ion exchangeable aluminosilicate glass of claim 27, wherein the glass is ion exchanged to a depth in a range from 20 μm up to 150 μm.
 29. The ion exchangeable aluminosilicate glass of claim 28, wherein the glass has an outer layer having a compressive stress of at least 200 MPa.
 30. The ion exchangeable aluminosilicate glass of claim 27, wherein the glass further comprises at least one of K₂O, Rb₂O, and Cs₂O, wherein P₂O₅≦[Σ(R₂O)—Al₂O₃].
 31. The ion exchangeable aluminosilicate glass of claim 25, wherein the glass is ion exchanged to a depth in a range from 20 μm up to 150 μm.
 32. The ion exchangeable aluminosilicate glass of claim 25, wherein the glass has an outer layer having a compressive stress of at least 200 MPa.
 33. The ion exchangeable aluminosilicate glass of claim 25, wherein the glass further comprises at least one of K₂O, Rb₂O, and Cs₂O, wherein P₂O₅≦[Σ(R₂O)—Al₂O₃].
 34. The ion exchangeable aluminosilicate glass of claim 25, wherein the aluminosilicate glass is an alkali aluminosilicate glass comprising: at least 59.24 mol % SiO₂; greater than 11.09 mol % Al₂O₃; 0-15 mol % B₂O₃; 1-10 mol % P₂O₅; 3-25 mol % Na₂O; and 0-5 mol % K₂O. 